The Keen Boulder is a sandle-like shoe, which features an open strap design.
The Keen Boulder’s straps are stiff enough to keep your foot securely centered over the sole even when negotiating a hill. The underfoot features ample padding on the ergonomic footbed, and a rubber outsole that sticks to rocks like a suction cup.

The fact that the Keen Boulder has an open strap design means that debris can get in as well as you can get nasty mosquitoe bites, but the trade off is ultimate breathability.
The Keen Boulder shoe is a suitable outdoor gear for canoeists and kayakers who wants a better alternative to regular flimsy sandels.